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On the Issue of Excess Lower Stratospheric Subtropical Transport in GEOS-DASIn recent years, data assimilation has become an indispensable tool for our understanding of the global features of meteorological variables. However, assessments of transport characteristics using trajectory related methods as well as chemical transport models (CTMs) show that results derived from assimilated (or analyzed) winds exhibit significantly larger mixing and entrainment rates compared to results derived from GCM winds, which are closer to results derived from observations (e.g., Douglass et al., 2002; Schoeberl et al., 2002). This discrepancy presents a serious challenge to our ability to understand and model global trace gas transport and distribution. We use the GEOS-DAS to explore this issue by examining how the process of data assimilation alters the dynamics of the underlying GCM and how this leads to the excess of lower stratospheric mixing and transport in the subtropics. In particular, we show that significant model biases in tropical winds necessitate large analysis increments. These increments directly force large subtropical regions of instability with negative PV gradient on the one hand, and generate excessive noise in the tropical wind fields on the other. The result is an excess of transport in the lower stratospheric subtropics.
Document ID
20030108651
Acquisition Source
Goddard Space Flight Center
Document Type
Conference Paper
Authors
Tan, Wei-Wu
(Science Applications International Corp. Greenbelt, MD, United States)
Geller, Marvin
(State Univ. of New York Stony Brook, NY, United States)
Pawson, Steven
(Maryland Univ. Baltimore County Catonsville, MD, United States)
Date Acquired
August 21, 2013
Publication Date
January 1, 2002
Subject Category
Meteorology And Climatology
Meeting Information
Meeting: American Geophysical Union Fall Meeting
Location: San Francisco, CA
Country: United States
Start Date: December 6, 2002
End Date: December 10, 2002
Sponsors: American Geophysical Union
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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